The color of the suit echoes the color scheme of his provocative, idiosyncratic, stylized and critically praised production, which stars Christopher Walken, Irene Worth, Moses Gunn, Keith David and Paul Hecht and which is at the Public Theater as the sixth play in the New York Shakespeare Festival`s Shakespeare Marathon.

''Coriolanus,'' one of Shakespeare`s later plays, tells of Roman politics in the 5th Century B.C. and of a brilliant military leader (played by Walken) whose pride prevents him from pandering to the public`s mob mentality and eventually leads to his downfall.

In this production, which also has been singled out for the high quality of its ensemble acting, the text has been greatly slashed, the movement of all the actors has been sharply and explicitly choreographed to a percussive score, the modern, gangsterlike costumes are almost all black and the set consists essentially of about a dozen black straight-backed chairs.

''My main objective was for utter clarity,'' Berkoff says, sitting over a cup of tea in the lobby of his Manhattan hotel. ''I had this obsession with Shakespeare being clear, since I`ve never seen a production in my life that was clear, apart from Peter Brook`s `Midsummer Night`s Dream` and a `Macbeth` in German done by Heiner Muller.

''I`ve always seen it muddied through,'' he says, ''usually with a leading actor, who has the greatest clarity, surrounded by acolytes. And the fact of having a star-figure surrounded by little plebes is part of the English colonial system-the royalty, the imperialist power, in a sense, of one star, and the rest sort of living on the fringe. And the way the theater came to reflect that was usually by someone saying, `Wouldn`t it be nice to have Sir This or Sir That playing this role?`

''Something I`ve always disliked intensely is the role of the spear carrier. A leading actor is speaking, and around him there`s five guys standing still-a lot of weary actors leaning on one leg, bored out of their heads and trying to look rather benignly bemused.

''So having been brought up on what I call imperialist theater, I was determined that the small parts should be equally important as the large. My conception was to take all the small parts of this play and organize them as a union.

''So I took all the tiny parts and tried to make them into a concept of a corps, almost like a corps de ballet, a theater machine. In the ballet, while the leading ballerina is doing things, the corps de ballet is often also creating a tapestry or a fresco of movement.

''In this production, they`re moving, coexisting, influencing, being a structure, being a part of it-and that`s a unity. It`s a kind of socialism of the theater and of existence.''

Berkoff defends the extensive cuts he made in the text against any complaints by purists.

''I think I did the audience a favor,'' he says. ''To cut less of it would have been onerous. The greatest service anyone can do to Shakespeare in his longer plays is to shape them and cut out a lot of extraneous verbiage.'' ''The Shakespeare must be right for the time,'' he continues. ''The play now, with an interval, lasts three hours. And 2 3/4 hours of text is already longer than `Macbeth.` When the actors first did a reading of the play at rehearsal it was 4 1/2 hours long.

''There are ancient Greek metaphors and comparisons that the audience would no longer be in touch with, and an enormous number of superfluous reiterations. And to make an audience sit through that today would be intolerable, no matter how you tried to make it clear.

''Maybe in Elizabethan times they were prepared to do that; they had more intervals, they cut up some fruit and they came back.''

Directing ''Coriolanus,'' a very warlike play, was not itself without battles and difficulties-difficulties for which Berkoff says he takes responsibility.

During rehearsals, he scolded the lighting designer, Stephen Strawbridge

(who resigned), and the costume designer, Martin Pakledinaz (who left and later returned). Relations with the set designer, Loren Sherman, were unhappy, too.

''There`s always teething troubles when you start a production in a new country, where you`re not familiar with the methods,'' Berkoff says. ''I have certain ways of working, and those ways have helped me over the years. And it is a very streamlined way, a very economical way. Costumes and decoration to me are almost peripheral, and they probably thought it was more central-and of course it is.

''In that way I was wrong,'' he says. ''They were being very helpful. They came with ideas and costumes, and I wasn`t able to give them the focus of importance that they should have had.''

But Berkoff rejects the system of ''most traditional theater, which is the kind of theater which we loosely call naturalism,'' in which, he says, the costumes and sets come first-they are givens that the director must deal with and in which ''you filter the actors through the set and that`s it.''

''What this tends to do is to deny the flow and imaginative direction that the actors may take.''